The Vancouver Aquarium says it will stop displaying whales, dolphins and porpoises, citing shifting public attitudes and a protracted community debate that has become a serious impediment to the organization's objectives.

Circumstances, as well as continuing protest, pushed the aquarium to back away from its long-time position that the captive creatures served a scientific and educational purpose. The aquarium, which became the first in the world to stop capturing wild cetaceans in 1996 following a Park Board directive, had lost all but one of them to illness in the past three years.

Thursday's announcement comes after years of dispute that involved the aquarium, local government and thousands of community members who made both their support and opposition known in chants and on placards waved outside the aquarium and in countless Park Board meetings. Supporters said the aquarium does important research in ocean conservation while opponents countered that it's unethical to hold intelligent marine mammals in tanks.

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"What used to be a distraction had become a more serious impediment to us achieving our mission," aquarium president and chief executive officer John Nightingale said. "It's time."

The aquarium will continue to pursue a judicial review of a May, 2017, decision by the Park Board to ban the facility from bringing in new cetaceans – an action the aquarium has argued it had no authority to take. A reversal would allow the aquarium to house rescued cetaceans before they are transported to another facility.

"We would like from time to time, on a temporary basis, to occasionally be able to use aquarium facilities in the rescue process, if that is required, as overseen by [the Department of Oceans and Fisheries]," Dr. Nightingale said.

Five cetaceans have died at the aquarium in a 15-month span: Chester, a false killer whale, died last November; Daisy, a harbour porpoise, last June; Aurora and Qila, mother and calf beluga whales, nine days apart in November, 2016; and Jack, a harbour porpoise, in August, 2016.

That leaves Helen, a Pacific white-sided dolphin, as the lone cetacean at the Stanley Park facility. The aquarium also owns five beluga whales that are currently on breeding loans in the United States: three at SeaWorld, one at Shedd Aquarium in Chicago and one at the Georgia Aquarium.

Helen is a senior-aged dolphin with only partial flippers and is not suitable for release into the wild, the aquarium said. That leaves two options: send her to another facility, which could pose health risks, or bring in a companion in violation of the Park Board ruling.

"We don't know what the answer is yet," Dr. Nightingale said. "Neither one of those options is 100-per-cent terrific."

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An animal-care team will weigh out the options and inform the public when a decision is made.

The decision also affects a $100-million upgrade to the aquarium, of which $45-million has already been spent. Its Canada's Arctic exhibition, which was to include huge tanks to accommodate more belugas, will be redesigned with smaller pools. Construction is slated to begin in the fall.